The invention relates to clutch plates or clutch discs in general, and more particularly to improvements in clutch plates or clutch discs (hereinafter called clutch plates) with several sets of energy storing elements installed between an input member and an output member. Such clutch plates can be used with advantage in friction clutches for motor vehicles, in hydrokinetic torque converters and in many other types of torque transmitting apparatus.
German Auslegeschrift No. 1 750 of Adachi (published Jul. 6, 1972) and German patent application No. 1 675 143 of Poteschil (published Dec. 3, 1990) disclose clutch plates of the type wherein two sets of energy storing elements in the form of coil springs are installed in the windows of a rotary input member (such input member can include a substantially disc-shaped carrier of friction linings) and a rotary output member (such output member can include a flange) and are designed to store energy when at least one of the input and output members leaves a neutral position and is rotated to assume one of two end positions relative to the other of these members. The aforementioned German publications further disclose projections which are provided on one of the input and output members and engage abutments on the other of the input and output members in each of the two end positions of at least one of the two members relative to the other member. The flange-like output member is rigid with the hub of the clutch plate, and the input member is assembled of two parts, namely the aforementioned carrier of friction linings and a disc which is spaced apart from and is rigidly connected to the carrier. The flange is located between the disc and the carrier and is provided with windows for the energy storing elements; such energy storing elements further extend into windows which are provided therefor in the carrier and in the disc. The projections are constituted by rivets or bolts which connect the disc to the carrier and are received, with limited freedom of movement in the circumferential direction of the input and output members, in recesses which are provided in the flange.
It is further known to install the carrier of friction linings between two discs which are rigidly connected to each other, either by bolts or rivets or by lugs which are integral parts of one of the discs and extend axially of the clutch plate into recesses of the other disc. The carrier has slots for the lugs of the one disc; the surfaces bounding the slots of the carrier act as abutments to determine the extent of angular movability of the carrier relative to the discs and vice versa.
German patent application No. 31 49 656 of Beccaris (published Jul. 15, 1992) discloses a clutch plate wherein a disc-shaped carrier of friction linings is connected with a second disc by a set of distancing elements in the form of rivets or bolts. The distancing elements extend through slots which are provided in the flange radially inwardly of energy storing elements in the form of coil springs which are received in windows of the carrier, disc and flange. The flange is rotatable relative to the hub of the clutch plate against the opposition of a relatively weak additional or auxiliary damper.
A drawback of presently known clutch plates, including the aforediscussed clutch plates, is that all of the projections (be they in the form of bolts, rivets or lugs) are supposed to simultaneously engage the associated abutments in each of the two end positions of the input and output members relative to each other. In other words, all of the projections are to participate in stoppage of the input and output members in each of the two end positions. This creates problems because the input and output members as well as the projections and the abutments for the projections are not, and cannot always be, made and machined or finished with a degree of precision which is required to ensure that each of a number of projections will invariably engage an adjacent abutment when the input and output members assume their first and/or second end positions, i.e., exactly upon completion of maximum angular movement of one of the input and output members relative to the other member in a clockwise or in a counterclockwise direction. Consequently, and as a rule, only one projection or a small number of projections will actually bear against the adjacent abutment or abutments in either of the two end positions of the input and output members relative to each other. This, in turn, enhances the likelihood of breakage of and/or excessive wear upon certain relatively weak sections or portions of that member which is provided with the recesses (e.g., in the form of slots or cutouts) for the projections of the other member. Furthermore, lack of a high degree of accuracy in the configuration and/or mounting or positioning of the projections and/or of the abutments for such projections can result in radial stressing of the input and output members, i.e., one or more projections are likely to move the member which is provided with the recesses away from a position of exact concentricity with the other member. This, too, can entail extensive wear upon and can reduce the useful life of a clutch plate.
Additional problems are likely to arise when the energy storing elements of a damper in a clutch plate include relatively weak and relatively strong energy storing elements. Thus, if a relatively weak portion of the input member and/or of the output member is simultaneously acted upon by a strong spring, by a weak spring and by a projection, such weak portion is likely to break after a relatively short period of use of the clutch plate.